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<refentry xml:id="gearmanclient.addtaskbackground" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>GearmanClient::addTaskBackground</refname>
  <refpurpose>Add a background task to be run in parallel</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <modifier>public</modifier> <type>GearmanTask</type><methodname>GearmanClient::addTaskBackground</methodname>
   <methodparam><type>string</type><parameter>function_name</parameter></methodparam>
   <methodparam><type>string</type><parameter>workload</parameter></methodparam>
   <methodparam choice="opt"><type>mixed</type><parameter role="reference">context</parameter></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>unique</parameter></methodparam>
  </methodsynopsis>
  <para>
   Adds a background task to be run in parallel with other tasks.  Call this method for all the tasks
   to be run in parallel, then call <methodname>GearmanClient::runTasks</methodname> to
   perform the work.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>function_name</parameter></term>
     <listitem>
      <para>
       &gearman.parameter.functionname;
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>workload</parameter></term>
     <listitem>
      <para>
       &gearman.parameter.workload;
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>context</parameter></term>
     <listitem>
      <para>
       &gearman.parameter.context;
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>unique</parameter></term>
     <listitem>
      <para>
       &gearman.parameter.unique;
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   A <classname>GearmanTask</classname> object or &false; if the task could not be added.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Two tasks, one background and one not</title>
    <para>
     This example illustrates the difference between running a background task
     and a normal task.  The client adds two tasks to execute the same function,
     but one is added with <methodname>addTaskBackground</methodname>.  A callback is 
     set so that progress of the job can be tracked.  A simple worker with an
     artificial delay reports on the job progress and the client picks this up
     through the callback.  Two workers are run for this example.  Note that the
     background task does not show in the client output.
    </para>
    <programlisting role="php">
<![CDATA[
<?php

# The client script

# create our gearman client
$gmc= new GearmanClient();

# add the default job server
$gmc->addServer();

# set a couple of callbacks so we can track progress
$gmc->setCompleteCallback("reverse_complete");
$gmc->setStatusCallback("reverse_status");

# add a task for the "reverse" function
$task= $gmc->addTask("reverse", "Hello World!", null, "1");

# add another task, but this one to run in the background
$task= $gmc->addTaskBackground("reverse", "!dlroW olleH", null, "2");

if (! $gmc->runTasks())
{
    echo "ERROR " . $gmc->error() . "\n";
    exit;
}

echo "DONE\n";

function reverse_status($task)
{
    echo "STATUS: " . $task->unique() . ", " . $task->jobHandle() . " - " . $task->taskNumerator() . 
         "/" . $task->taskDenominator() . "\n";
}

function reverse_complete($task)
{
    echo "COMPLETE: " . $task->unique() . ", " . $task->data() . "\n";
}

?>
]]>
    </programlisting>
    <programlisting role="php">
<![CDATA[
<?php

# The worker script

echo "Starting\n";

# Create our worker object.
$gmworker= new GearmanWorker();

# Add default server (localhost).
$gmworker->addServer();

# Register function "reverse" with the server.
$gmworker->addFunction("reverse", "reverse_fn");

print "Waiting for job...\n";
while($gmworker->work())
{
  if ($gmworker->returnCode() != GEARMAN_SUCCESS)
  {
    echo "return_code: " . $gmworker->returnCode() . "\n";
    break;
  }
}

function reverse_fn($job)
{
  echo "Received job: " . $job->handle() . "\n";

  $workload = $job->workload();
  $workload_size = $job->workloadSize();

  echo "Workload: $workload ($workload_size)\n";

  # This status loop is not needed, just showing how it works
  for ($x= 0; $x < $workload_size; $x++)
  {
    echo "Sending status: " . ($x + 1) . "/$workload_size complete\n";
    $job->sendStatus($x+1, $workload_size);
    $job->sendData(substr($workload, $x, 1));
    sleep(1);
  }

  $result= strrev($workload);
  echo "Result: $result\n";

  # Return what we want to send back to the client.
  return $result;
}

?>
]]>
    </programlisting>
    <para>
     Worker output for two workers running:
    </para>
    <screen>
<![CDATA[
Received job: H:foo.local:65
Workload: !dlroW olleH (12)
1/12 complete
Received job: H:foo.local:66
Workload: Hello World! (12)
1/12 complete
2/12 complete
2/12 complete
3/12 complete
3/12 complete
4/12 complete
4/12 complete
5/12 complete
5/12 complete
6/12 complete
6/12 complete
7/12 complete
7/12 complete
8/12 complete
8/12 complete
9/12 complete
9/12 complete
10/12 complete
10/12 complete
11/12 complete
11/12 complete
12/12 complete
12/12 complete
Result: !dlroW olleH
Result: Hello World!
]]>
    </screen>
    <para>
     Client output:
    </para>
    <screen>
<![CDATA[
STATUS: 1, H:foo.local:66 - 1/12
STATUS: 1, H:foo.local:66 - 2/12
STATUS: 1, H:foo.local:66 - 3/12
STATUS: 1, H:foo.local:66 - 4/12
STATUS: 1, H:foo.local:66 - 5/12
STATUS: 1, H:foo.local:66 - 6/12
STATUS: 1, H:foo.local:66 - 7/12
STATUS: 1, H:foo.local:66 - 8/12
STATUS: 1, H:foo.local:66 - 9/12
STATUS: 1, H:foo.local:66 - 10/12
STATUS: 1, H:foo.local:66 - 11/12
STATUS: 1, H:foo.local:66 - 12/12
COMPLETE: 1, !dlroW olleH
DONE
]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><methodname>GearmanClient::addTask</methodname></member>
    <member><methodname>GearmanClient::addTaskHigh</methodname></member>
    <member><methodname>GearmanClient::addTaskLow</methodname></member>
    <member><methodname>GearmanClient::addTaskHighBackground</methodname></member>
    <member><methodname>GearmanClient::addTaskLowBackground</methodname></member>
    <member><methodname>GearmanClient::runTasks</methodname></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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